This invention relates to a vehicle driveshaft and more particularly, to a relatively stiff vehicle driveshaft which is relatively light in weight and which includes relatively long splined portions having relatively large and/or wide spline pitch diameters and working areas.
A vehicle driveshaft is typically and operatively mounted to a transmission assembly and to a differential assembly and, more particularly, transfers the transmission produced torque to the differential, thereby causing the vehicle wheels to be desirably and selectively turned. The driveshaft also dynamically compensates for the change or modification in the distance between the transmission and the differential which occurs as the vehicle is driven. Hence, the driveshaft includes a portion or a member which typically and telescopingly moves along the longitudinal axis of the driveshaft in response to relative movement between the differential and the transmission (e.g., the driveshaft is capable of dynamically modifying its length in response to the movement of the vehicle).
This dynamic length modification is typically achieved by the use of a pair of splined members which are normally manufactured of a relatively heavy material, such as conventional and commercially available iron, and which are respectively and commonly referred to as the xe2x80x9cslip yokexe2x80x9d and the xe2x80x9cyoke shaftxe2x80x9d. Particularly, the yoke shaft member is selectively inserted into the slip yoke and is movably coupled to the transmission. The slip yoke is typically coupled to the differential and the respective splines of these members (which are typically broached or xe2x80x9cmachinedxe2x80x9d onto the yoke members) intermeshingly cooperate to allow and/or to cause the yoke shaft to rotate the slip yoke in response to the rotation of the transmission, thereby allowing the transmission produced torque to be selectively coupled to the differential by the rotation of the slip yoke. The intermeshed splines also allow the yoke shaft to be movable along the longitudinal axis of the driveshaft, thereby allowing the driveshaft to dynamically compensate for changes in the distance between the transmission and the differential and allowing the driveshaft to desirably operate as the vehicle is driven. While these driveshafts allow for the desired communication of the transmission-produced torque to the differential, they suffer from some drawbacks.
First, the yoke members of these prior driveshafts are normally and rather loosely connected because the respective splines are typically formed on only relatively small or relatively short portions of the respective and relatively heavy yoke members. These relatively short intermeshing splined portions allow the engaged members to undesirably xe2x80x9cwobblexe2x80x9d as the vehicle is driven and produce undesirable noise and vibrations which are undesirably communicated into the passenger compartment. These relatively short xe2x80x9cyoke engagementxe2x80x9d portions also cause undesirable xe2x80x9cbacklashxe2x80x9d to occur as the transmission generated torque is transferred to the slip yoke member. Secondly, the relatively heavy yoke members require relatively narrowly formed and narrowly spaced splines which cause the engaged members to experience relatively high stress and loads and which further cause undesirable fatigue and/or failure of the splines and/or of the engaged yoke members. Additionally, the relatively heavy material used to form the yoke members requires the yoke members to have a relatively small diameter to avoid the undesirable addition of weight to the vehicle. These relatively small diameter members further cooperatively provided only a relatively limited or small amount of xe2x80x9cengagingxe2x80x9d surface or xe2x80x9cworkingxe2x80x9d area between the intermeshing yoke members, thereby further causing relatively high stress and loads to be applied and/or transferred among and between the engaged members. Finally, the engaged yoke members are prone to undesirably xe2x80x9cbucklexe2x80x9d during and/or as a result of a vehicle accident, thereby undesirably damaging many of the vehicle underbody components, including but not limited to, the vehicle fuel tank.
There is therefore a need for a new and improved vehicle driveshaft which overcomes many, if not all, of the previously delineated drawbacks of such prior vehicle driveshafts.
It is a first object of the invention to provide a vehicle driveshaft which overcomes at least some of the previously delineated drawbacks of prior vehicle driveshafts.
It is a second object of the invention to provide a relatively lightweight vehicle driveshaft having a pair of selectively hardened, engaging, and intermeshing splined members which cooperatively allow for the formation of a relatively stiff vehicle driveshaft.
It is a third object of the invention to provide a vehicle driveshaft having a pair of selectively engaging and intermeshing splined members, each of the splined members respectively containing relatively long and relatively widely spaced splines which form and/or which contain relatively wide or large space width and/or xe2x80x9cworking areasxe2x80x9d.
It is a fourth object of the invention to provide a vehicle driveshaft having a pair of selectively engaging and intermeshing splined members which are respectively engaged and/or are operatively coupled along a relatively long engagement and/or coupling distance.
It is a fifth object of the invention to provide a vehicle driveshaft having a pair of intermeshing splined members having a respective and a relatively large diameter.
According to a first aspect of the present invention, a vehicle driveshaft is provided and includes a pair of aluminum members, each of the aluminum members being of a certain respective length and having a certain respective diameter of a certain respective value. Each of the pair of aluminum members has a respective splined portion which has a respective length equal to about three times the value of one of the respective diameters and the respective splined portions intermeshingly cooperate to form a relatively stiff vehicle driveshaft.
According to a second aspect of the present invention, a method is provided to increase the stiffness of a driveshaft of the type having a first member, and a second member which movably extends a certain length within the first member. The method includes the steps of increasing the certain length.
According to a third aspect of the present invention, a vehicle driveshaft is provided and is formed by the process of providing a first and a second aluminum member; forming splines within the first and the second aluminum members; coating the formed splines with a hard anodized coating; and placing the first member into the second member, thereby cooperatively forming a driveshaft by the use of the first and the second members.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.